The present invention relates to a novel process for preparing 2-(1-chloro-cycloprop-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2,4-triazole-5-thiono-1-yl)-propan-2-ol, which is known as an active compound with microbicidal, in particular fungicidal, properties.
It is already known that 2-(1-chloro-cycloprop-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2,4-triazole-5-thiono-1-yl)-propan-2-ol can be prepared by initially reacting 3-chloro-2-(1-chloro-cycloprop-1-yl)-1-(2-chloro-phenyl)-propan-2-ol with hydrazine hydrate, if appropriate in the presence of an inert organic solvent, such as alcohol, ether or nitrile, then reacting the resulting 2-(1-chloro-cycloprop-1-yl)-3-(2-chloro-phenyl)-2-hydroxy-propyl-1-hydrazine with formaldehyde and alkali metal thiocyanate or ammonium thiocyanate and finally reacting the resulting 2-(1-chloro-cycloprop-1-yl)-1-(2-chloro-phenyl)-2-hydroxy-3-(1,2,4-triazolidine-5-thiono-1-yl)-propane with oxygen in the presence of sulphur and potassium hydroxide (cf. WO 99-18 087). The reaction sequence can be illustrated by the formula scheme below: 
This process has the disadvantage that the hydrazine compound formed in the first step is relatively unstable in the free state. Moreover, it is unfavourable that undesirable by-products are formed in the course of the multi-step synthesis and that the yield is relatively low for a preparation on an industrial scale. Finally, it is likewise detrimental that an interfering overoxidation can take place during the third step, resulting in the elimination of sulphur from the target product.
It has now been found that 2-(1-chloro-cycloprop-1-yl)-1-(2-chloro-phenyl)-3-(4,5-dihydro-1,2,4-triazole-5-thiono-1-yl)-propan-2-ol of the formula 
can be prepared when
a) in a first step, 2-(1-chloro-cycloprop-1-yl)-2-(2xe2x80x2-chloro-benzyl)-oxirane of the formula 
xe2x80x83is initially reacted with hydrazine hydrate in the presence of aromatic hydrocarbon, if appropriate in a mixture with acetonitrile, and hydrogen chloride is then introduced, or the mixture is extracted with aqueous hydrochloric acid
b) in a second step, the resulting 2-(1-chloro-cycloprop-1-yl)-3-(2-chloro-phenyl)-2-hydroxy-propyl-1-hydrazine hydrochloride of the formula 
xe2x80x83is then treated with alkali metal hydroxide in the presence of water and in the presence of aromatic hydrocarbon, if appropriate in a mixture with a lower alcohol, or in the presence of alkyl alkylcarboxylate, and then reacted successively with formaldehyde and thiocyanate of the formula
Xxe2x80x94SCNxe2x80x83xe2x80x83(IV), 
in which
x represents sodium, potassium or ammonium,
xe2x80x83in the presence of water and in the presence of aromatic hydrocarbon, if appropriate in a mixture with a lower alcohol, or in the presence of alkyl alkylcarboxylate and, if appropriate, in the presence of a catalyst, and
c) in a third step, the resulting 2-(1-chloro-cycloprop-1-yl)-1-(2-chloro-phenyl)-2-hydroxy-3-(1,2,4-triazolidine-5-thiono-1-yl)-propane of the formula 
xe2x80x83is then reacted with iron(III) chloride in the presence of aqueous hydrochloric acid and in the presence of an inert organic diluent.
It is extremely surprising that the triazolinethione derivative of the formula (I) can be prepared by the process according to the invention in higher yields than by the prior-art methods. It is also unexpected that, during the course of the multi-step synthesis, there are virtually no interfering side reactions.
The process according to the invention has a number of advantages. Thus, as already mentioned, it allows the synthesis of the triazolinethione derivative of the formula (I) in high yield. Moreover, it is favourable that the starting materials and reaction components required can be prepared in a simple manner and are available even in relatively large amounts. It is a further advantage that the individual reaction steps and the isolation of the reaction products can be carried out without any difficulties. Finally, it should also be mentioned that the hydrazine hydrochloride derivative of the formula (III), in contrast to the corresponding hydrazine compound, can be handled without any stability problems, and that an overoxidation in the last step can be avoided.
Using sodium hydroxide as neutralizing agent and sodium thiocyanate and Formalin solution as reaction components for carrying out the second step, the course of the process according to the invention can be illustrated by the following formula scheme: 
The 2-(1-chloro-cycloprop-1-yl)-2-(2xe2x80x2-chloro-benzyl)-oxirane of the formula (II) required as starting material for carrying out the process according to the invention is know n (cf. EP-A 0 297 345). It can be prepared by reacting the chlorohydrin derivative of the formula 
in the presence of an acid binder, such as potassium tert-butoxide, sodium methoxide or potassium carbonate, and in the presence of a diluent, such as dimethylformamide, methanol, n-butanol, tetrahydrofuran, methyl-tert-butyl ether or toluene, at temperatures between 20xc2x0 C. and 60xc2x0 C.
When carrying out the first step of the process according to the invention, the oxirane of the formula (II) can be employed both in pure form and in a mixture with the chlorohydrin derivative of the formula (VI).
Aromatic hydrocarbons suitable for carrying out the first step of the process according to the invention are preferably benzene, toluene or xylene. Particular preference is given to using toluene in a mixture with acetonitrile. It is very particularly advantageous to use acetonitrile in an amount which is equimolar to that of the oxirane of the formula (II).
Both the first step and the second and third steps of the process according to the invention are generally carried out under atmospheric pressure. However, it is also possible to work under elevated pressure or, if no gaseous components take part in the reaction, even under reduced pressure.
When carrying out the first step of the process according to the invention, the reaction temperatures can be varied within a certain range. In general, the first step is carried out at temperatures between 20xc2x0 C. and 150xc2x0 C., preferably between 60xc2x0 C. and
For carrying out the first step of the process according to the invention, in general from 3 to 6 mol of hydrazine hydrate are employed per mole of oxirane of the formula (II). Specifically, oxirane of the formula (II), if appropriate in a mixture with chlorohydrin of the formula (VI), is reacted with hydrazine hydrate in the presence of toluene and, if appropriate, in the presence of an amount of acetonitrile which is equivalent to that of the oxirane of the formula (II). Work-up is then carried out by customary methods. In general, the reaction mixture is cooled to room temperature and is mixed with water, the organic phase is separated off and washed with water and an equivalent amount or else an excess of dry hydrogen chloride gas is then introduced with cooling. The resulting solid is separated off, washed with toluene, if appropriate in a mixture with a further hydrocarbon, and dried. However, it is also possible to extract the mixture with aqueous hydrochloric acid. The resulting solid is separated off, washed with toluene, if appropriate in a mixture with a further hydrocarbon, and dried.
In a preferred variant, both the first and the second step of the process according to the invention are carried out under an atmosphere of protective gas. Preferred protective gases are argon and nitrogen.
The alkali metal hydroxide used for carrying out the second step of the process according to the invention is preferably lithium hydroxide, sodium hydroxide or potassium hydroxide. Particular preference is given to using sodium hydroxide.
Preferred aromatic hydrocarbons used as diluents for carrying out the second step of the process according to the invention, both in the treatment of the hydrazine hydrochloride derivative of the formula (III) and in the subsequent reaction with formaldehyde and thiocyanate of the formula (IV), are benzene, toluene and xylene. Preferred lower alcohols are methanol, ethanol or propanol. The preferred alkyl alkylcarboxylate is ethyl acetate. Particularly preferably, both the neutralization and the subsequent reaction in the second step of the process according to the invention are carried out either in the presence of toluene in a mixture with ethanol or in the presence of ethyl acetate.
The formaldehyde required as reaction component for carrying out the second step of the process according to the invention can be employed as paraformaldehyde, as gaseous formaldehyde or else as Formalin solution (=aqueous formaldehyde solution). Preference is given to using Formalin solution.
The preferred thiocyanate for carrying out the second step of the process according to the invention is sodium thiocyanate.
Suitable catalysts for carrying out the second step of the process according to the invention are all reaction accelerators which are customary for such reactions. Preference is given to using sodium hydrogen sulphate.
When carrying out the second step of the process according to the invention, the reaction temperatures can likewise be varied within a certain range. In general, both the neutralization of the hydrazine hydrochloride derivative of the formula (III) and the further reaction are carried out at temperatures between 0xc2x0 C. and 30xc2x0 C., preferably between 10xc2x0 C. and 25xc2x0 C.
When carrying out the second step of the process according to the invention, in general an equivalent amount or else an excess of alkali metal hydroxide, from 1 to 2 mol of formaldehyde and from 1 to 2 mol of thiocyanate of the formula (IV) and, if appropriate, from 1 to 2 mol of sodium hydrogen sulphate and water are employed per mole of hydrazine hydrochloride derivative of the formula (III), where the water may also be present in excess. Work-up is carried out by customary methods. In general, the reaction mixture is admixed with water, and the organic phase is separated off, washed with saturated aqueous sodium chloride solution and with water, dried and concentrated. Any impurities that may still be present can be removed by customary methods, such as recrystallization.
Preferred inert organic diluents for carrying out the third step of the process according to the invention are ethanol, ethyl acetate or mixtures of ethanol and toluene.
When carrying out the third step of the process according to the invention, the reaction temperatures can likewise be varied within a certain range. In general, the third step is carried out at temperatures between 0xc2x0 C. and 100xc2x0 C., preferably between 10xc2x0 C. and 65xc2x0 C.
When carrying out the third step of the process according to the invention, in general an equivalent amount or else an excess of iron(III) chloride is employed per mole of triazolidine compound of the formula (V). Work-up is carried out by customary methods. In general, if appropriate after prior admixing of the reaction mixture with water, the phases are separated and the organic phase is washed, dried and concentrated. Any impurities which may still be present can be removed by customary methods, for example by recrystallization.
In a particular variant, the process according to the invention can be carried out such that steps two and three are conducted as a one-pot reaction. In this case, the mixture obtained in the second step is subjected directly, without prior isolation of the triazolidine of the formula (V), to the oxidation in the third step. However, prior to the addition of the iron(III) chloride solution, the reaction mixture obtained in the second step has to be washed thoroughly with water to remove any excess thiocyanate which may be present.
The triazolinethione derivative preparable according to the invention can be present in the xe2x80x9cthionoxe2x80x9d form of the formula 
or in the tautomeric xe2x80x9cmercaptoxe2x80x9d form of the formula 
For the sake of simplicity, only the xe2x80x9cthionoxe2x80x9d form is shown in each case.
The triazolinethione derivative preparable according to the invention is known as an active compound having microbicidal, in particular fungicidal, properties (cf. WO 96-16 048).
The practice of the process according to the invention is illustrated by the examples below.